Continuing to be defiant, North Korea warned the world on Tuesday that sanctions the U.N. demands "mean a war," as South Korea continued its effort to find a peaceful solution to the nuclear standoff by sending another top diplomat to Washington.

South Korea's national security adviser will meet with his U.S. counterpart, Condoleezza Rice, among other White House officials in Washington. He will then travel to Tokyo for more talks with South Korea's other key ally.

North Korea's announcement comes a day after U.N. nuclear watchdog decided to give North Korea a second chance to abandon its suspected weapons program -- effectively delaying any U.N. sanctions against the reclusive, communist regime.

In the message carried by the official state-run North Korean News Agency, North Korea railed against claims it was an international missile threat. The isolated country also demanded the United States apologize for what it described as "piracy" in the seizure last month of a North Korean ship carrying missiles to Yemen.

It described the seizures as a part of a U.S. strategy of "total economic sanctions aimed at isolating and stifling" North Korea. Washington has proposed sanctions in the current nuclear standoff.

Last month, U.S. and Spanish warships seized a North Korean ship carrying Scud missiles in the Arabian Sea. They later allowed it to sail after receiving assurances the Scuds would not be transferred elsewhere in the tense Persian Gulf region.

To pressure North Korea on the nuclear issue, U.S. officials have also considered encouraging the country's neighbors to reduce economic ties with Pyongyang as punishment if the situation does not improve.

China, North Korea's last major ally, appealed Tuesday for a negotiated settlement, but a Foreign Ministry spokeswoman wouldn't say whether Beijing is willing to intervene with the isolated nation.

"We hope to see a settlement of the issue through dialogue," said ministry spokeswoman Zhang Qiyue. Asked several times at a news briefing about what China would do to encourage the North to seek such a settlement, she would say only that Beijing "maintains contact with all sides."

In its message Tuesday, North Korea criticized the United States for portraying it as an international missile threat and retorted: "The U.S. tops the world's list in producing and selling the weapons of mass destruction."

The reaction came as South Korean envoys upped efforts to persuade the United States to open dialogue with the communist state.

Washington assured envoys from Seoul and Tokyo on Monday that the United States would work closely with them to ease the crisis and had no plans to attack North Korea.

"We have no intention of invading North Korea," President Bush told reporters in the White House.

Hours earlier, the International Atomic Energy Agency approved a resolution giving the North another chance to back down from its nuclear standoff with the West. But the watchdog's chief, Mohamed ElBaradei, warned North Korea the matter would be turned over to the U.N. Security Council if it does not abandon its weapons program and readmit inspectors it expelled last month.

Referring the issue to the Security Council is a last resort for the IAEA and could lead to punitive sanctions or other actions against North Korea's regime.

The South Korean government welcomed the decision on Tuesday, saying in a Foreign Ministry statement that it offered North Korea a "precious chance" to resolve the issue "diplomatically and peacefully."

Meanwhile, South Korean media reported that a possible compromise plan, being floated by Seoul, would require North Korea to abandon its uranium-based nuclear program and the United States to resume fuel oil shipments suspended in December.

If the United States resumes the shipments, North Korea would have no justification for reactivating its second, plutonium-based nuclear program, according to reports.

Verifying North Korea compliance, however, is still a hurdle.

South Korea's Yim has said his discussions with White House officials would focus on setting "a broad framework of methodology rather than looking for a specific solution."

Later this week, U.S. Assistant Secretary of State James Kelly is to travel to Seoul.

The North alarmed the world in October by admitting to a U.S. envoy that it had a secret uranium-based nuclear weapons program, in violation of a 1994 accord.

As punishment, the United States and its allies halted oil supplies promised in the agreement. North Korea then announced it would reactivate its older plutonium-based nuclear program, saying it needs to restart a reactor to generate electricity.

The United States says the plutonium-based program could be used to build nuclear weapons. Washington has also indicated North Korea may already have two nuclear weapons and can build several more in short order.

The Associated Press contributed to this report.